1. Field of the Invention
The present invention relates to a headlamp for a vehicle that has a discharge bulb.
2. Prior Art
In most headlamps for vehicles, a lamp unit provided with a light source bulb therein is tiltably installed in a lamp chamber that is formed by a lamp body and a front lens. Recently, a discharge bulb capable of high luminance irradiation has been employed as the light source bulb for vehicular headlamps.
In the meantime, in a headlamp for a vehicle, lighting of the light bulb increases the temperature of the front lens; and the thus heated front lens can melt snow that covers the outer surface of the front to lens some extent.
However, when a discharge bulb is used as the light source bulb, the temperature increase of the front lens is less compared to a halogen lamp used in conventional cases. Accordingly, the snow that covers the front lens freezes without melting even if there is not much snow. As a result, it is necessary to frequently remove the snow from the front lens.
In view of the foregoing problems with prior art lamps, the object of the present invention is to provide a headlamp for a vehicle that can effectively prevent freezing of the front lens of a vehicular headlamp that contains a discharge bulb.
More specifically, in view of the fact that a lighting circuit unit is provided in a headlamp that uses a discharge bulb, the present invention accomplishes the object by utilizing the heat generated by the lighting circuit.
More specifically, the present invention is a headlamp for a vehicle that comprises a light chamber formed by a lamp body and a front lens with a lamp unit provided with a discharge bulb being tiltably disposed in the light chamber, and the headlamp is characterized in that:
at the lower end of the lamp body, a unit housing chamber that houses a lighting circuit unit for lighting the discharge bulb is formed so as to be adjacent to the light chamber with a separation wall in between, and
at the front portion of the separation wall, a communicating opening is formed so that the interior space of the unit housing chamber communicates with the interior space of the light chamber.
In the above, the xe2x80x9clamp unitxe2x80x9d may be a so-called projector type lamp unit, or it can be a reflector unit that has a discharge bulb installed in an ordinary reflector.
Also, the xe2x80x9cunit housing chamberxe2x80x9d may be of a structure in which its main part is formed by the lamp body, or it can be a casing that is mounted to the lamp body.
Furthermore, the xe2x80x9cfront portion of the separation wallxe2x80x9d is meant to be a position where the communicating opening is formed and the air heated in the unit housing chamber by the lighting circuit can flow into the front space of the lamp chamber through the communicating opening. In other words, the xe2x80x9cfront portionxe2x80x9d is a position which is closer to the front than the central portion in the longitudinal direction of the separation wall.
As seen from the above, the headlamp of the present invention comprises a light chamber formed by the lamp body and front lens and a lamp unit that includes a discharge bulb is tiltably installed in the light chamber; and at the lower end of the lamp body, a unit housing chamber that houses the lighting circuit unit for lighting the discharge bulb is formed so as to be adjacent to the light chamber with the separation wall in between, and at the front portion of the separation wall, a communicating opening that allows the interior space of the unit housing chamber to communicate with the interior space of the light chamber is formed.
Accordingly, when the discharge bulb is lit, heat is generated in the lighting circuit unit; and as a result, heated air fills the inside of the housing chamber. Then, the heated air flows into the light chamber through the communicating opening which is formed in the separation wall. Since the communicating opening is located in the front portion of the separation wall, heated air flows into the front space of the light chamber and heats the front lens. Thus, the front lens heated by the heated air and therefore having an increased temperature can melt and remove the snow that covers the outer surface of the front lens.
Accordingly, freezing of the front lens is effectively prevented.
In the above structure, an extension reflector may be provided in the light chamber so that it is over the communicating opening and the front end thereof extends to the vicinity of the inner surface of the front lens. As a result, the heated air flowing into the light chamber through the communicating opening can be forcedly guided to the inner surface of the front lens along the bottom surface of the extension reflector. Thus, freezing of the front lens can be prevented more effectively.